Which is most abundent enzyme on earth?

Series of enzymes involved in the given reactions of ${\mathrm{C}}_3$ cycle

(i) $\mathrm{A}\left[6\mathrm{c}\right]+\mathrm{B}\left[3\mathrm{c}\right]\to \mathrm{C}\left[4\mathrm{c}\right]+\mathrm{D}\left[5\mathrm{c}\right]$

(ii) $\mathrm{C}\left[4\mathrm{c}\right]+\mathrm{E}\left[3\mathrm{c}\right]\to \mathrm{F}\left[7\mathrm{c}\right]$

(iii) $\mathrm{D}\left[5\mathrm{c}\right]\to \mathrm{G}\left[5\mathrm{c}\right]$

(iv) $\mathrm{G}\left[5\mathrm{c}\right]+\mathrm{ATP}\to \mathrm{H}\left[5\mathrm{c}\right]$

In photosynthetic carbon-fixation, which one of the following reacts with ${\mathrm{CO}}_2$

Which among the following statements are correct?
(i) The quantum yield of photosynthesis decreases with an increase in temperature in ${\mathrm{C}}_3$ plants, as compared to ${\mathrm{C}}_4$ plants.
(ii) The first stable product in ${\mathrm{C}}_3$ pathway is phosphoglycerate, whereas in the ${\mathrm{C}}_4$ pathway it is oxaloacetate.
(iii) ${\mathrm{C}}_3$ pathway is present only in ${\mathrm{C}}_3$ plants and ${\mathrm{C}}_4$ pathway is present in all plants.

(iv) The rate of photorespiration is very high in ${\mathrm{C}}_4$ plants and very low in ${\mathrm{C}}_3$ plants.